A sub-assembly of the above kind is described in the specification of U.S. Pat. No. 4,574,932 and the corresponding French published patent application FR 2 524 097A. Such a sub-assembly is commonly referred to as a "friction cassette".
In the above mentioned United States patent specification, snap-fitting means are arranged between the resilient gripping means and the spacing ring. To this end, the spacing ring has resiliently deformable lugs which, in practice, are separate elements from the axial projections of the spacing ring. As a result, the resilient gripping means are exposed to the outside, in such a way that they can become damaged under various circumstances, and in particular when being transported.
In addition, the spacing ring is quite complicated, because it has, firstly, axial projections, and secondly, resiliently deformable lugs. In addition, the holes that have to be formed in the guide ring to accommodate the resilient lugs and projections tend to weaken that ring.